Thiomarinol is a novel hybrid antibiotic produced by \(Pseudoalteromonas\) \(rava\) sp. nov. SANK 73390. It is structurally similar to a clinically significant antibiotic mupirocin, but includes an additional pyrrothine moiety joined to the mupirocin-like marinolic acid via an amide bond. Thiomarinol has been shown to be more potent against a wider range of microorganisms. This potency was hypothesised to be due to either an increase in inhibition of its target enzyme, isoleucyl-tRNA synthetase (IleS) or an increase in antibiotic uptake and/or inefficient efflux by bacterial cells or a combination of both. This thesis describes experiments that investigate the basis for this increase in potency.